Rare Plant Profile – Mountain Lady’s Slipper (Cypripedium montanum Dougl. ex Lindl.)
Mountain lady’s slipper (Cypripedium montanum) is a perennial herb in the Orchidaceae Family. Its leafy stems emerge from underground rhizomes to grow 20-50 cm tall. Leaves are alternate, egg-shaped to broadly lance-shaped with many parallel veins. Two or three sweet-scented flowers are found near the end of the stem. Flowers are white and purple, or purplish green in colour, with 3 lance-shaped sepals, 2 narrowly lance-shaped, twisted petals, spreading to the sides, with a broad, white-pouched lower lip petal that has an egg-shaped, purple-dotted, yellow lobe at the mouth of the pouch. Another similar species that also has a white-pouched lower lip is the sparrow’s-egg lady’s slipper (Cypripedium passerinum Richards.) but this more common species has much smaller flowers with flat petals and short, egg-shaped sepals. Small native bees pollinate the flowers by crawling into the pouch, transferring pollen as they do so.
In Canada, mountain lady’s slipper can be found in moist, open coniferous, deciduous, and mixedwood forests, and forest openings in the montane regions of British Columbia, Alberta, and Saskatchewan. Note that there is some uncertainty as to the natural origin of the Saskatchewan population found in the Cypress Hills. The conservation status rank of mountain lady’s slipper is G4 (Apparently Secure) globally, N4N5 (Apparently Secure) nationally, and S2 (Imperiled) provincially. In Alberta, this ranking is due to habitat loss, fire suppression, harvesting of wild plants, grazing pressures, disturbances due to construction and incidental loss due to the collection of other wild species. Due to their small extent, populations of mountain lady’s slipper can be easily destroyed and rarely survive being transplanted.
The ANPC is excited to announce plans to publish the Rare Vascular Plants of Alberta 2nd Edition by June 2022 if everything goes according to plan. The project has been made possible by countless volunteer hours over the past 6 years as well as external grant funding sources, and ANPC donations and membership fees. Please consider renewing your membership, donating, and telling your friends and colleagues about the ANPC so they can consider becoming members, to help provide continued support to initiatives such as this.
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Photos by L. Allen
 Kershaw, L.; Gould, J.; Johnson, D.; Lancaster, J. 2001. Rare vascular plants of Alberta. Univ. Alberta Press, Edmonton, Alberta and Nat. Resour. Can., Can. For. Serv., North. For. Cent., Edmonton, Alberta